In order to improve light extraction efficiency of a flip-chip light-emitting diode (LED) and realize single polarization light output, three models of normal, flip-chip and integrated metal sub-wavelength grating flip-chip LED were established. RSOFT software was used to simulate and optimize the device, and theoretical analysis and simulation verification were carried out. The results show that, flip-chip LED can improve the light extraction efficiency, but it is very sensitive to the thickness of P-GaN layer and can not output single polarized light. Flip-chip LED integrated with metal sub-wavelength grating can achieve single polarized light output without the influence of P-GaN layer thickness; this kind of LED can output stable polarized light, but it is heavily affected by grating parameters and thickness of transition layer. The thickness of transition layer and parameters are very significant. By optimizing the structure, the extraction efficiency can reach 57.63% and the polarization extinction ratio can reach 25.8dB. The research has some guidance for manufacturing blue ray LED with high performance.